The United Nations' health agency reiterated that the risk of passengers transmitting the Ebola virus during air travel is low. Still, anyone with an illness or symptoms typical of the highly virulent disease shouldn't be allowed to travel unless it's for appropriate medical care, the agency said in a statement.

Symptoms of Ebola include a sudden fever, intense weakness, muscle pain, headache and sore throat. This is followed by vomiting, diarrhea, rash, poor kidney and liver function and, in some cases, both internal and external bleeding.

Unlike diseases such as tuberculosis or flu, Ebola isn't spread by breathing air from an infected person. Transmission requires direct contact with blood, secretions, organs or other body fluids of infected living or dead persons or animals, the agency said.

"Travelers are, in any event, advised to avoid all such contacts and routinely practice careful hygiene, like hand washing," the agency said.

The latest WHO figures put the death toll from the outbreak at nearly 1,070, with approximately 2,000 confirmed cases. At this point, Ebola cases have been reported in Guinea, Liberia, Sierra Leone and, to a lesser extent, Nigeria.

But, the magnitude of the Ebola outbreak in West Africa may be far greater than current statistics indicate, WHO officials reported Friday.

Patients were flooding treatment centers that have just opened, and the recorded case and death tolls may "vastly underestimate the magnitude of the outbreak," said WHO spokesman Gregory Hartl, the Associated Press reported.

Ebola has a mortality rate approaching 90 percent, according to WHO officials.

The U.S. Centers for Disease Control and Prevention has been providing computer software and hardware to the countries hit hardest by Ebola, so officials there can track and analyze the outbreak's spread in real time, WHO added.

Meanwhile, the husband of one of two U.S. aid workers infected with Ebola while in West Africa has been declared healthy following the completion of a 21-day quarantine. In a statement released Monday, David Writebol said he was reunited Sunday with his wife, Nancy Writebol, who continues to undergo intensive medical care at Emory University Hospital in Atlanta.